Broadly, an embodiment of the present invention generally relates to a device and a continuous process for heating wood for the purpose of eradicating burrowed pests such as gypsy moths and emerald ash borer beetles. Firewood as well as wood pallets and skids used for transporting other goods are particularly susceptible to gypsy moths and emerald ash borer beetle infestation since they are not heat treated in the course of the manufacturing so as to cause the extermination of these pests. Some state laws prohibit transporting infested wood across state lines and out of quarantined areas.
The eradication of gypsy moths and emerald ash borer beetle infestation in wood is currently carried out in wood kilns where the temperature in the center of the wood is raised to at least 160° F. and held there for at least 75 minutes. Heating may be supplied by electricity, hot water, steam and fire. A certification process by the Center of Plant Health and Science Technology requires obtaining internal wood temperature sensors placed in several representative locations that are accurate within +/−0.5° F. The use of a wood drying kiln to eradicate gypsy moths and emerald ash borer beetles in fire wood and pallets is slow and expensive. Other processes approved by state laws such as fumigation and debarking are equally problematic. Fumigation involves the use of chemicals that are toxic to the environment and to humans. While debarking is effective, a large amount of non-bark material is lost from the firewood in the process. Heat treatment is effective because it kills bugs and mold and also dries the firewood, resulting in lighter loads.
Prior art relevant to this invention includes U.S. Pat. No. 5,341,580 that discloses a process for drying wood strands for the manufacture of oriented strand board comprising the steps of: feeding wood strands onto a belt conveyor to form a bed of strands; conveying the wood strands on the belt conveyor through a dryer housing in a substantially continuous manner; heating a quantity of drying air to a desired temperature; passing the drying air through the bed of strands in the dryer housing; and after passing the drying air through the bed of strands, discharging the wood strands from the dryer housing. U.S. Pat. No. 6,163,981 discloses a process and apparatus for drying material, especially wood particles, having moisture therein, and comprising depositing the material to a selected depth onto a transport conveyor at the first end of a drying chamber. Heat is applied to the material as it is transported toward the opposite second end of the drying chamber so that, adjacent the second end, the material forms essentially two layers, a first layer having a first level of moisture therein and a second layer having a second level of moisture therein which is different from the moisture content of the first layer. Means are provided adjacent the second end for removing the second layer, which has the desired moisture, from the conveyor and directing that layer exteriorly of the chamber. U.S. Pat. No. 6,678,994 relates to a process of eradicating pests by the controlled application of heat for a predetermined period of time. U.S. Pre-grant publications No. 20060272172 and 200700443431 teach a dual path kiln having one or more chambers and at least two lumber charge paths adapted to convey lumber through the kiln in opposite directions. U.S. Pre-grant publication No. 200700443431 is a continuation of U.S. Pre-grant publication No. 20060272172. U.S. Pre-grant publications No. 20080127548 refers to a process for killing insect pests in wood, comprising the steps of: a) disposing wood in a vacuum-tight container having a flexible wall; b) evacuating the container such that the flexible wall presses against the wood; and c) performing step (b) until the insect pests in the wood are killed.